I don't think the 6 weeks vs. 3 years tells the full story. C++ collects up a whole truck load of changes and waits up to 3 years then dumps all of them in one go. Whereas Rust releases them individually, waiting up to six weeks after they've done baking in the nightly compiler (though they've likely been in development for years before that).
That's not to say Rust is necessarily slower paced than C++ either, just that a raw number on release dates aren't helpful by themselves.
Major C++ releases and Rust Editions are both on three year cycles.
AFAIK rust editions are not on any schedule currently, there's no guarantee that there'll be a Rust 2021 edition.
Re:How often does Rust change?
by steveklabnik on Saturday April 11, 2020 @04:29PM
(#22843989)
Yes. We have not technically committed to a Rust 2021 yet. We are going to decide this year.
Re:How often does Rust change?
by iknowstuff on Saturday April 11, 2020 @03:47PM
(#22843733)
Yup. If you read the linked article, you’ll notice the release schedule was addressed by the author.
C++ pretty much didn't change between 1998 and 2011 though (2003 was mostly a bugfix and compatibility release). And these days it updates every 3 years (you forgot C++14 though it was a very minor release) which is a much slower pace than Rust's 6 weeks cycle.